1. Technical Field
The present invention relates to a technique of performing screen display control.
2. Related Art
In the related art, a printing apparatus including a liquid crystal display for displaying a menu image or an input photographic image, such as a printing apparatus disclosed in JP-A-2007-235189 (paragraph 0021, FIG. 1 and so on), is known. This type of printing apparatus includes a screen display control device which processes image data and has a video memory (videoRAM) for temporarily storing the processed data, and periodically reads the processed image data stored in the video memory so as to perform a screen display on the liquid crystal display. However, in a recent liquid crystal display, the capacity of image data displayed on the liquid crystal display increases with high resolution and high gradation. Accordingly, in order to store the image data with the increased capacity, the capacity of the video memory needs to increase and thus cost increases. In order to solve such a problem, a technique of compressing image data by a known data compression method such as predictive coding (DPCM coding) of a difference between adjacent pixel data and storing the compressed data in a video memory is known. In addition, at the time of the screen display, the compressed data is read from the video memory and is expanded so as to restore original image data. Accordingly, it is possible to switch an image displayed on a screen by replacing the compressed data stored in the video memory with compressed data of a new image.
However, the liquid crystal display includes two types of liquid crystal displays such as so-called landscape scan type and portrait type scan type liquid crystal displays, but, recently, the dedicated portrait scan type liquid crystal display for a mobile telephone is mass-produced with low cost as a general-purpose product. Accordingly, in order to reduce manufacturing cost of a product such as a printing apparatus including a liquid crystal display, this portrait scan type liquid crystal display is desired to be employed. However, if a landscape type image in which the arrangement order of pixel data configuring image data differs is displayed on the portrait scan type liquid crystal display, this landscape type image data needs to be stored in a video memory after converting the configuration of the image data (the arrangement order of the pixel data) so as to be matched to a scan direction of the portrait scan type liquid crystal display.
However, since the data compressed using the difference between the adjacent pixel data of the image data is stored in the video memory, if a portion of the compressed data is rewritten, original image data cannot be restored and the compressed data stored in the video memory cannot be partially rewritten to new image data. Accordingly, since the pixel data is sequentially stored at a proper position of the video memory from leading pixel data of the input landscape type image data, the landscape type image data cannot be converted into the portrait type data configuration. Therefore, when the portrait type image stored in the video memory as the compressed data is replaced with the image data of the newly input landscape type image, first, the portrait type image data of one screen matched to the scan direction of the portrait scan type liquid crystal display needs to be formed by rearranging the pixel data configuring the input landscape type image data.
That is, after the landscape type image data is converted into the portrait type image data and the converted image data is stored in a buffer memory, the converted portrait type image data needs to be compressed by a compression unit and the compressed image data needs to be stored in the video memory. At this time, in order to form line data of each line of the portrait type image data, since a portion of the line data of every line of the input landscape type image data is necessary, all the input landscape type image data needs to be temporarily stored in the buffer memory. Accordingly, in order to convert the landscape type image data into the portrait image data, the buffer memory for storing at least the image data of one screen before compression is necessary. Thus, the cost is increased by employing the portrait scan type liquid crystal display with low cost.